This invention relates to a heavy-duty electric switch of the gas current blow-out type which includes a stationary compression cylinder provided, at one end, with a stationary nozzle made of an electrically insulating material. In the cylinder there is coaxially arranged a stationary hollow contact pin. The switch further comprises an annular piston which can be driven into the compression cylinder for compressing the gas therein and which is mechanically coupled with a movable hollow contact pin cooperating with the stationarily supported hollow contact pin. During opening of the switch, the movable hollow contact pin is displaced in the same direction as the piston.
Switches of the above-outlined types are known and are disclosed, for example, in German Laid-Open Application (Offenlegungsschrift) No. 2,316,009. In contradistinction to other gas current blow-out switches which in most cases have a driven nozzle, the above-named Offenlegungsschrift discloses a stationarily arranged nozzle. The driven member, in turn, is a compression piston for compressing the gaseous extinguishing medium, in most cases SF.sub.6 which, during opening of the switch, moves in a cylinder in the direction of the nozzle. When a predetermined pre-compression has been reached, contact separation takes place. The movable contact which is mechanically coupled to the piston and is moved by the same mechanism, is displaced in the same direction as the piston and is separated from the stationary contact supported in the cylinder.